The present invention relates to a miniature gas turbine engine and, more particularly, to mounting of a rotor shaft therefore.
Miniature gas turbine or turbojet engines (typically of 100 lbf thrust and smaller) are often utilized in single usage applications such as reconnaissance drones, cruise missiles, decoy and other weapon applications, including air-launched and ground-launched weapon systems. The use of such an engine greatly extends the range of the weapon in comparison to the more conventional solid fuel rocket engine. Miniature gas turbine engines are difficult to fabricate economically for general expendable usage in large numbers.
The array of programs and potential programs are now often entitled by the defense department with words such as “Low Cost” and “Affordable”. To achieve economically feasible extended range expendable propulsion sources, it is necessary that the gas turbine engines be manufactured relatively inexpensively yet provide a high degree of reliability and efficiency. Component that greatly affects performance yet are rather complicated to manufacture are the rotating components, such as the rotor system which typically includes a shaft mounted turbine and compressor wheel.
Rotor systems of miniature gas turbine engines typically operate at greater than 100,000 rpm which requires precisely machined surfaces and interfaces to minimize friction and assure balanced operation. Furthermore, the rotor shaft and turbine wheel are subjected to relatively high temperatures which may be damaging to the bearing system which supports the rotor system. Typically, miniature rotor systems carry over much technology from the conventional main thrust engine and APU market. Although effective and reliable, such engine technology may be too expensive for application to a miniature gas turbine engine. Conversely, existing turbo charger applications often utilized in the commercial model aircraft industry provide inexpensive components but generally fail to meet the high altitude starting, performance and reliability requirements demanded of defense programs.
Accordingly, it is desirable to provide an uncomplicated and inexpensive rotational system for a miniature gas turbine engine.